Ivermectin - Truth About Its Formulation

 Ivermectin
Chemical Composition and the Truth About Its Formulation

Ivermectin is one of the most widely discussed antiparasitic medications in recent years. Two common questions often arise: What exactly is it chemically made of, and have manufacturers recently added controversial inactive ingredients such as Polysorbate 80 and Titanium Dioxide to the tablets?

Here is a clear, evidence-based overview based on official pharmaceutical data.

Chemical Composition of Ivermectin

Ivermectin is not a single pure molecule. It is a semi-synthetic mixture of two closely related compounds derived from natural avermectins produced by the soil bacterium Streptomyces avermitilis.

The two components are:

Component	Full Name	Molecular Formula	Molecular Weight	Typical Proportion
Major	22,23-dihydroavermectin B₁a	C₄₈H₇₄O₁₄	≈ 875.1 g/mol	≥ 80–90%
Minor	22,23-dihydroavermectin B₁b	C₄₇H₇₂O₁₄	≈ 861.1 g/mol	≤ 10–20%

• The only structural difference between the two is the side chain at the C-25 position (sec-butyl in B₁a versus isopropyl in B₁b).
• Both belong to the 16-membered macrocyclic lactone class.
• CAS number for the mixture: 70288-86-7.

Ivermectin is produced by selectively hydrogenating the C22–C23 double bond of natural avermectin B1. Official specifications (including FDA-approved products) require a high proportion of the B₁a component.

Do Human Oral Ivermectin Tablets Contain Polysorbate 80 or Titanium Dioxide?

A claim has circulated that manufacturers have “now” added Polysorbate 80 and Titanium Dioxide to Ivermectin tablets. This claim does not hold up when checked against official product labels.

Current inactive ingredients in human oral tablets:

Stromectol (brand-name, Merck): Microcrystalline cellulose, pregelatinized starch, magnesium stearate, butylated hydroxyanisole (BHA), and anhydrous citric acid.

Common generic 3 mg tablets (U.S. examples): Colloidal silicon dioxide, croscarmellose sodium, magnesium stearate, microcrystalline cellulose, and pregelatinized starch.

Neither Polysorbate 80 nor Titanium Dioxide appears on these lists. These formulations have remained consistent for years, with no evidence of a recent reformulation that introduced the two ingredients.

Where These Ingredients Actually Appear

Formulation Type	Polysorbate 80	Titanium Dioxide	Notes
Human oral tablets (Stromectol & generics)	No	No	Official FDA/DailyMed labels
Ivermectin 1% topical cream (rosacea treatment)	Yes (in some versions)	No	Used as an emulsifier
Veterinary pastes (e.g., horse paste)	Sometimes	Frequently	Titanium dioxide is used as a white colorant

The circulating claim appears to result from confusion between different product types — particularly mixing human oral tablets with veterinary pastes or topical creams.

Summary

• Chemically, Ivermectin is a well-defined mixture of two macrocyclic lactones (primarily B₁a with a smaller amount of B₁b).
• Standard human oral tablets do not contain Polysorbate 80 or Titanium Dioxide according to current official labeling.
• Claims that these ingredients were recently added to the tablets are not supported by regulatory documents.

For the most accurate information about any specific product, always refer to the package insert or the official FDA DailyMed entry for that exact manufacturer and NDC number.